New percutaneous approaches for chronic total occlusion of coronary arteries

Novel treatment of a totally occluded venous outflow tract of an arteriovenous graft

INTRODUCTION

Conventional guidewire techniques are not always sufficient to restore arteriovenous graft patency in patients with challenging vascular scenarios. We discuss a novel approach to the treatment of chronic total occlusion of the venous outflow tract to enable successful arteriovenous graft thrombectomy.

CASE PRESENTATION

A 28-year-old female with end-stage renal disease on chronic hemodialysis and recurrent arteriovenous graft thromboses presented with a clotted thigh graft. An existing ipsilateral common femoral vein stent was found to be chronically occluded, causing persistent venous outflow obstruction and rendering an initial attempt at thrombectomy unsuccessful due to wire buckling and the inability to navigate through the stent chronic total occlusion.

RESULTS

After establishing femoral vein access, a vibrational recanalization device was used to cross the occluded stent. The device was then removed, permitting routine angioplasty. Post-angioplasty angiogram revealed persistent intra-stent stenosis, so a covered stent was deployed with good angiographic results. Routine pharmaco-mechanical thrombectomy of the arteriovenous graft was then performed. Two additional stents were placed due to stenotic recoil in the venous limb of the graft. Angioplasty was also performed at the arteriovenous graft arterial anastomosis. Repeat imaging demonstrated marked improvement in the graft blood flow.

DISCUSSION

Total occlusion of the venous outflow tract prevents adequate blood flow through an arteriovenous graft and undermines successful thrombectomy. We describe the use of the Crosser vibrational recanalization device for the safe and effective treatment of a chronic total occlusion of the venous outflow tract, thus extending the life of the patient's vascular access for hemodialysis.

Increased susceptibility of arterial tissue to wire perforation with the application of high-frequency mechanical vibrations

High-frequency mechanical vibrations (20-50 kHz), delivered via small diameter flexible wire waveguides represent a minimally invasive technology for the treatment of chronic total occlusions and in other tissue ablation applications. Tissue disruption is reported to be caused by repetitive mechanical contact and cavitation. This work focuses on the effects of vibrating wire waveguides in contact with arterial tissue. An apparatus with clinically relevant parameters was used, characterized as operating at 22.5 kHz and delivering amplitudes of vibration of 17.8-34.3 μm (acoustic intensity, I(SATA): 1.03-3.83 W/cm(2)) via 1.0-mm diameter waveguides. Inertial cavitation (in water at 37 °C) was determined to occur above amplitudes of vibration greater than 31.4 μm (I(SATA) = 3.21 W/cm(2)). The energized waveguides were advanced through tissue samples (porcine aorta) and the force profiles were measured for a range of acoustic intensities. The results show that the tissue perforation initiation force, perforation initiation energy, and total energy required to perforate the tissue reduces with increasing acoustic intensity. No significant reduction in perforation force or energy was observed in the inertial cavitation region. Multistage perforation was evident through the force profile and histological examination of the tissue samples post wire waveguide perforation.

[Usefulness of the Tornus® catheter in nondilatable coronary chronic total occlusion]

The treatment of coronary chronic total occlusions (CTO) remains a challenge for the interventional cardiologist. Failure of balloon angioplasty is the second more common cause of an unsuccessful procedure. We describe our experience with the use of the new Tornus® catheter (Asahi Intecc, Aichi, Japan) designed specifically for the treatment of "nondilatable" CTO. Between November 2008 and March 2010, 17 patients (age 62 years, 88% men, 82% dyslipidemia, 52% hypertension, 29% diabetes) were treated in whom balloon dilatation had failed after crossing the lesion with the guide. The use of Tornus® catheter was successful without complications in 15. All patients underwent clinical follow-up (median, 573 days) with no documented major adverse events. The use of the Tornus® catheter is safe and feasible in those patients with CTO lesions in whom balloon angioplasty has been unsuccessful.

Stenting of complex lesions: an overview

Contemporary management of coronary artery disease relies increasingly on percutaneous techniques combined with medical therapy. Although percutaneous coronary intervention (PCI) can be performed successfully in most lesions, several difficult lesion subsets continue to present unique technical challenges. These complex lesions may be classified according to anatomic criteria, including extensive calcification, thrombus, and chronic occlusions, or by location, such as bifurcations, saphenous vein grafts and unprotected left main. PCI of these lesions often requires novel devices, such as drug-eluting stents, hydrophilic guidewires, distal protection balloons or filters, thrombectomy catheters, rotational atherectomy, and cutting balloons. An integrated approach that combines these devices with specialized techniques and adjunctive pharmacologic agents has greatly improved PCI success rates for these complex lesions.

The feasibility and safety of applying the Magnetic Navigation System to manage chronically occluded vessels: a single centre experience

AIMS

Applying the Magnetic Navigation System (MNS) to manage chronic total occlusions (CTOs). The MNS precisely directs a magnetised guidewire in vivo through two permanent external magnets.

METHODS AND RESULTS

The first 43 consecutive MNS treated CTOs were retrospectively evaluated. Computed tomography coronary angiography (CTCA) co-integration with the MNS provided a virtual road map through the occlusion. Unsuccessful MNS cases were managed with bailout conventional guidewire techniques. Experienced CTO and MNS operators had unrestricted access to CTO devices and equipments. The MNS crossing success increased from 40% to 56% over 52 months and averaged 44.2% (19/43 patients). In 58.3% (14/24) of failed MNS cases the conventional wire approach was successful, giving an overall procedural success rate of 76.6%. Of those conventionally treated, two patients required pericardiocentesis. On average, 1.8 ± 0.9 stents (lengths 44.7 ± 21.4 mm and diameter 2.8 ± 0.4 mm) were implanted. Procedural times were lengthy (125.0 ± 35.3 min) requiring high fluoroscopy dosage (11980.2 ± 6457.9 Gy/cm2) and contrast media usage (388.8 ± 170.2 ml). Operators persevered less with magnetic wires (20.9 ± 12.4 min vs. 27.7 ± 24.4 min), and preferentially used the least stiff wire as first choice (53.5%). CTCA co-integration did not influence procedural outcome. As with conventional wires, higher magnetic wire successes occurred in low calcified lesions, those with a central stump and without bridging collaterals.

CONCLUSIONS

In unselected CTOs, the magnetic wires are safe and feasible. Current modest success rates with a high procedural bailout rate implicate the need for improved magnetic guidewire technology comparable to available sophisticated conventional CTO wires. Randomised studies are needed to clarify the value of magnetic guided recanalisation.

Reverse STAR for retrograde recanalisation in a chronic total coronary artery occlusion present for 21 years

Reopening chronic total occlusions (CTOs) has been shown to alleviate anginal symptoms as well improve left ventricular ejection fraction. In patients with previous coronary artery bypass grafts, management of CTOs may avoid the need for repeat surgery. A variety of techniques have been described including subintimal tracking and re-entry (STAR) and CART approaches. The anatomy and the length of time that a CTO is present can determine whether it can be reopened. The present report describes a variation on the STAR technique used to open a CTO present for 21 years.

Comparison of safety, efficacy, and outcome of successful versus unsuccessful percutaneous coronary intervention in "true" chronic total occlusions

Despite improving techniques for opening chronic total occlusions (CTOs), the benefit of successful recanalization of the artery remains unclear. The aims of this study were to investigate the safety and efficacy of percutaneous coronary intervention for "true" CTO, defined by Thrombolysis In Myocardial Infarction (TIMI) flow grade 0 and duration > or =3 months, and to compare the outcome of successful versus failed procedures. A cohort of 172 consecutive patients with de novo CTOs of native vessels confirmed by angiographic review in which percutaneous coronary interventions were attempted was studied. End points included angiographic success, in-hospital complications, and long-term major adverse cardiac events. Technical success was obtained in 73.8% of CTO lesions (127 of 172). No deaths or nonfatal Q-wave myocardial infarctions occurred in the hospital. Repeat percutaneous coronary interventions in the hospital were required in 1.6% of patients (2 of 127) in whom the CTOs were initially opened. Perforation during the initial failed attempts occurred in 6.7% of patients (3 of 45). One patient required operative repair. After an average follow-up period of 2 years, patients with successful procedures experienced similar incidences of cardiac death and nonfatal Q-wave myocardial infarctions as did patients with failed procedures (5.3% and 4.9%, respectively, p = 0.3). Patients with successfully opened arteries required target vessel revascularization more frequently, but this did not reach statistical significance (18.8% vs 0%, p = 0.06). In conclusion, attempts to open CTOs with the devices available at the time of this registry were accompanied by a significant risk for perforation. Furthermore, successful recanalization did not translate into a reduction in 2-year mortality or nonfatal Q-wave myocardial infarctions compared with patients with failed procedures.